Synthesis and characterisation of new oligoacetylenic silanes

Synthetic routes to a series of novel oligoacetylenic silanes with or without (hetero)aromatic bridges have been developed. The compound Me₃SiC≡CSi(Ph)₂C≡CSiMe₃ was first prepared, which was selectively desilylated with CaCO₃ in methanol at room temperature to afford the mono-protected bis(alkynyl) silane Me₃SiC≡CSi(Ph)₂C≡CH in moderate yield. Treatment of this mono-protected species with ⁿBuLi, followed by silylation with Ph₂SiCl₂, gives a good yield of Me₃SiC≡CSi(Ph)₂C≡CSi(Ph)₂ C≡CSi(Ph)₂C≡CSiMe₃, with alternating silicon and acetylene units. A range of linear silicon-linked oligoalkynes containing phenylene, bithienylene and anthrylene rings, HC≡CRC≡CSi(Ph)₂C≡CRC≡CH and HC≡CRC≡CSi(Ph)₂C≡CRC≡CSi(Ph)₂ C≡CRC≡CH (R = 1,4-phenylene, 5,5′-bithienylene or 9,10-anthrylene), were synthesised by condensation reactions of Ph₂SiCl₂ with the components obtained in situ from a HC≡CRC≡CH-ⁿBuLi mixture in THF and the products were isolated by chromatography on silica. All these new compounds have been characterised by IR, ¹H and ¹³C NMR and UV/VIS spectroscopies and mass spectrometry. The single-crystal X-ray structure of HC≡C(p-C₆H₄)C≡CSi(Ph)₂C≡C (p-C₆H₄)C≡CSi(Ph)₂C≡C(p-C ₆H₄C≡CH has been determined, showing that two silicon atoms and six acetylene units constitute the backbone of the molecule.